Partially purified alkaline phosphatase from Bacillus subtilis SB15 appears to be an aggregate of several polypeptides (3-4) which dissociate on heating in presence of 3 percent sodium dodecyl sulfate (SDS). The aggregate requires high Mg ions (0.2M Magnesium acetate) for solubility. Antibody against enzyme protein from glucose grown cells cross reacts with both enzyme proteins obtained from 0.1 percent and 2 percent lactate grown cells. Surprisingly the enzyme from 2 percent lactate grown cell demonstrates a non-identity relationship to enzymes from glucose or 0.1 percent lactate grown cell. Vegetative alkaline phosphatase is derepressed by glucose and this $ derepression is reversed by 2 percent lactate. The glucose derepression starts after a long lag in late log phase of growth. The enzyme synthesis completes almost within one cell generation. The lag of enzyme synthesis in presence of 0.1 percent sodium lactate is longer than that in presence of glucose. Penicillinase (which is a constitutive membrane protein), synthesis in Bacillus licheniformis is unaffected by the variations of these carbon sources. Hence, the effect of glucose and lactate on alkaline phosphatase synthesis appears to be highly specific.